[kornish]

Correct. Previously, advertisers bought segments of 3P cookies, then targeted those IDs wherever they appeared. Cookiepocalypse means that advertisers will be unable to buy segments of domain-agnostic IDs (3P cookies), and so it will be up to the publisher to segment up its viewers and sell access to those segments to advertisers.

There will be more layers of aggregation on top of that, such as SSPs (supply-side platforms, which aggregate access to publishers' inventory) or PMPs (private marketplaes, which are effectively funnels of select inventory per some critera for some client), but the general principle is that targeting capabilities are shifting from the demand side to the supply side, closer to the viewer. So instead of picking the right segment, effective advertising will be about picking the right publishers. That's good for Google and Facebook because their 1P data is so rich.